Ever been frustrated by the fact that your javascript code can't make JSON requests to sites under other other domains? Well, WebSpeaks.in has some happy news for you in the form of JSONP.

Well.....finally i have worked out how to post cross-domain data which is restricted by browser's security policies. What is it?? This will be used for posting AJAX requests via java-script to any web-service or web-page in any DOMAIN and also get back the results from there.

JSONP allows you to call a URL outside of the domain the script is running from with a callback. This callback lives in the calling script so, technically, it never leaves that scope. There's lots of other resources out there to help you implement it in your own code including jQuery and Prototype JSON handling.

The application that we'll build in this article will allow you to enter a Twitter search term, and display the tweets received in Silverlight. Unfortunately, this process isn't as simple as loading a URL from Silverlight, because of something known as cross-domain access policy.

He talks some about the problem that this cross-domain access can cause for your scripts and how he used PHP to solve it. He created a simple web service that his Silverlight application could query in the same domain. This service did the call to Twitter and returned back the results to the waiting Silverlight app.